1. Field of the Invention
The present invention relates to a latent curing agent for epoxy resin and a curable epoxy resin composition having the same incorporated therein, and in particular to a curing agent for epoxy resin providing storage stability and low-temperature rapid curability to an epoxy resin composition, as well as a curable epoxy resin composition having the same incorporated therein which is excellent in storage stability and has low-temperature rapid curability.
Further, the present invention relates to a latent curing agent for epoxy resin and a curable epoxy resin composition which are suitable for application in the electronics field such as encapsulants for semiconductor, anisotropic conductive films, conducting composites, etc.
2. Background Prior Art
Based on the recent remarkable development in the field of electronics, the density of semiconductor element circuits has been rapidly increased and simultaneously, large-scale production thereof has become feasible, whereby the miniaturization and high-performance of electronic devices are now in rapid progress. Further, as these electronic devices become into wide use, improved workability and reduced costs in large-scale production have got demanded. Further, with respect to epoxy resin used as adhesive for these electronic devices and latent curing agent for such epoxy resin, there is a need for improved high-performance in various physical. properties. As a matter of course, the utilization of epoxy resin is not limited to this.
The epoxy resin composition includes a two-pack type which is used by mixing an epoxy resin as the main agent with a curing agent just before use and a one-pack type having an epoxy resin as the main agent previously mixed with a curing agent. Of the two, the one-pack type is preferably used because it can prevent erroneous formulation and enables machinery automation on line. For the one-pack type epoxy resin composition; is needed a so-called latent curing agent which does not react with the epoxy resin compound at room temperature, and is caused to react and cure upon heating.
As for the latent curing agent, some curing agents have been proposed so far, and typical examples thereof include dicyandiamide, dibasic acid dihydrazide, boron trifluoride amine complex salt, guanamines, melamine, imidazoles, etc. However, an epoxy resin composition resulting from mixing an epoxy compound with dicyandiamide, melamine or a guanamine is excellent in storage stability, but is disadvantageous in that it requires, for curing, a long time at high temperatures of 150xc2x0 C. or more. Further, such epoxy resin composition is often used in combination with a curing accelerator to reduce curing time. The addition of a curing accelerator indeed leads to a reduction in the curing time of the curing epoxy resin composition but causes such problem that the storage stability thereof is significantly deteriorated. The epoxy resin compositions having a dibasic acid dihydrazide or an imidazole incorporated therein as the latent curing agent, are cured at relatively low temperatures but poor in storage stability. The boron trifluoride amine complex is highly hygroscopic and exerts adverse effects on various characteristics of a cured product from an epoxy resin composition having said complex incorporated therein. In these circumstances, a latent curing agent for epoxy resin, which gives an epoxy resin composition excellent in storage stability with low-temperature rapid curability, is highly desired.
To improve or solve these problems, JP 56-155222A and JP 57-100127A propose curing agents wherein dialkyl amines are addition-reacted with epoxy compounds, and JP 59-53526A proposes curing agents wherein an aminoalcohol or aminophenol is addition-reacted with an epoxy compound. Further, U.S. Pat. Nos. 406,625 and 4,268,656 propose curing agents wherein imidazole compounds or N-methyl piperazine is addition-reacted with epoxy compounds at their secondary amino groups.
However, the curing agents described above do not sufficiently confer storage stability and low-temperature curability on epoxy resin compositions in which they have been incorporated. In particular, those epoxy resin compositions wherein bisphenol F type epoxy compounds or reaction diluents such as monoepoxy compounds or diepoxy compounds have been used, do not exhibit satisfactory storage stability.
Further, phenol resin, dicyandiamide, hydrazide compounds or the like have been used heretofore as a latent curing agent, but they require, for curing, heating treatment in an oven at 150 to 200xc2x0 C. for a long time. Recently, there is a need for rapidly curable resin compositions which can be cured in a short time, with the view of improving workability if the step of assembling semiconductor devices and reducing manufacturing costs. In addition, as circuits become highly densified on printed circuit boards, etc., a reduction in accuracy due to thermal stress upon high-temperature curing, has been worried about, and also from the viewpoint of energy costs, there has been a need for curing at relatively low temperatures to minimize the thermal history of printed circuit boards, etc.
As typical examples of latent curing agents with low-temperature rapid curing properties, e.g. amine adduct type latent curing agents are known and JP 9-92029A, for example, describes an example where a commercial latent curing agent xe2x80x9cAjicurexe2x80x9d (a product of Ajinomoto Co., Ltd.) is used as an conductive paste.
On the other hand, as semiconductor production technology rapidly advances, it has become impossible to ignore the physical properties of a curing agent per se incorporated in curable epoxy resin compositions as well as its effect on electrical reliability, and there has been a need for latent curing agents more suitable in the field of electronics than those conventionally used.
It is an object of the present invention to provide a latent curing agent which can give an epoxy resin composition excellent in storage stability and low-temperature rapid curable properties or curability, and furthermore, to a rapidly curable epoxy resin composition resulting from having the same mixed with an epoxy compound, which maintains excellent storage stability and is curable at relatively low temperatures, that is, 80 to 120xc2x0 C. in a short time.
Another object of the present invention is to provide a latent curing agent for epoxy resin and a curable epoxy resin composition, which have low-temperature rapid curing properties, are excellent in heat resistance, electrical reliability, etc., and are suitable in uses in the electronics field such as encapsulants for semiconductor, anisotropic conductive films, conducting composites, etc.
As a result of their eager study in view of the various problems described above, the present inventors have found that an addition product obtainable by addition reaction in the presence of water, with an epoxy compound, of a compound having in the molecule both a tertiary amino group and a functional group such as OH group, SH group, NH group, NH2 group, COOH group, CONHNH2 group or the like capable of reacting with an epoxy compound, gives when mixed with an epoxy compound, a curable epoxy resin composition superior in storage stability and low-temperature rapid curability. On the basis of these findings, the present inventors have completed a first invention.
Accordingly, the present invention relates to a latent curing agent for epoxy resin, comprising a reaction product obtainable by allowing the 2 kinds of compounds, that is, (A) an epoxy compound having more than one (1) epoxy groups on the average in the molecule and (B) a compound having in the molecule both a tertiary. amino group and at least one functional group selected from the group consisting of OH group, SH group, NH group, NH2 group, COOH group and CONHNH2 group, to react on each other in the presence of 0.05-5.0 equivalents of water per 1 equivalent of the epoxy group of Compound (A). Incidentally, it is added that with respect to the relationship in equivalence between epoxy group and water, 1 epoxy group corresponds to 1 water molecule.
The present invention also relates to a latent curing agent for epoxy resin, comprising a reaction product obtainable by allowing the 3 kinds of compounds, that is, (A) an epoxy compound having more than one (1) epoxy groups on the average in the molecule, (B) a compound having in the molecule both a tertiary amino group and at least one functional group selected from the group consisting of OH group, SH group, NH group, NH2 group, COOH group and CONHNH2 group, and (C) a compound having in the molecule at least one functional group selected from the group consisting of NH2 group and CONHNH2 group or in the molecule at least 2 functional groups selected from the group consisting of OH group, SH group, NH group, NH2 group, COOH group and CONHNH2 group (provided that a compound having an epoxy group or tertiary amino group in the molecule is excluded), to react on one another in the presence of 0.05 to 5.0 equivalents of water per 1 equivalent of the epoxy group of Compound (A).
Furthermore, the present invention relates to a curable epoxy resin composition comprising (x) an epoxy compound having more than one (1) epoxy groups on the average in the molecule and (y) the said latent curing agent for epoxy resin as the essential ingredients, and optionally, (z) inorganic filler(s).
Further, as a result of their eager study in view of the problems in the prior art as described above, the present inventors have found that a specific amine adduct-type latent curing agent has low-temperature rapidly curing properties and simultaneously, improves the heat resistance and electrical reliability of a product resulting from curing an epoxy resin composition as compared with a conventional one, and further improves electrical conductivity when used in conducting composites. On the basis of these findings, the present inventors have completed a second invention.
Accordingly, the present,invention relates to a latent curing agent for epoxy resin, comprising a reaction product of the following three kinds of compounds (a), (b) and (c):
(a) an alicyclic epoxy compound having 2 or more epoxy groups in the molecule;
(b) a compound having in the molecule both a tertiary amino group and at least one functional group selected from the group consisting of OH group, SH group, NH group, NH2 group, COOH group and CONHNH2 group; and
(c) a compound having in the molecule at least one functional group selected from the group consisting of NH2 group and CONHNH2 group or in the molecule at least 2 functional groups selected from the group consisting of OH group, SH group, NH group and COOH group (provided that a compound having an epoxy group or tertiary amino group in the molecule is excluded).
The present invention also relates to a latent curing agent for epoxy resin, comprising a reaction product of the following four kinds of compounds (a), (b), (c) and (d):
(a) an alicyclic epoxy compound having 2 or more epoxy groups in the molecule;
(b) a compound having in the molecule both a tertiary amino group and at least one functional group selected from the group consisting of OH group, SH group, NH group, NH2 group, COOH group and CONHNH2 group;
(c) a compound having in the molecule at least one functional group selected from the group consisting of NH2 group and CONHNH2 group or in the molecule at least 2 functional groups selected from the group consisting of OH group, SH group, NH group and COOH group (provided that a compound having an epoxy group or tertiary amino group in the molecule is excluded); and
(d) a glycidyl compound having 2 or more epoxy groups in the molecule.
Furthermore, the present invention relates to a curable epoxy resin composition comprising one of the said latent curing agents for epoxy resin and an epoxy compound having 2 or more epoxy groups in the molecule.
In addition, the present invention relates to a curable epoxy resin composition comprising one of the said latent curing agents for epoxy resin, an epoxy compound having 2 or more epoxy groups in the molecule, and inorganic filler(s).
The first and second inventions described above constitute, as can be seen from the foregoing and following description, a group of inventions so linked as to form a single general inventive concept.
Hereinafter, the present invention will be described in detail.
First, the first invention will be described.
Compound (A) as one of the starting materials for synthetic reaction of the inventive latent curing agent for epoxy resin, that is, an epoxy compound having more than one (1) epoxy group on the average in the molecule, is not particularly limited, and any epoxy compound having more than one epoxy group on the average in the molecule can be used.
For example, mention can be made of epoxy compounds having more than one epoxy groups on the average in the molecule, which are represented by any of the general formulae (1) to (3) below. Further, mention is made of, e.g., epoxy compounds having more than one epoxy groups on the average in the molecule that are on the alicyclic hydrocarbon ring and/or that are bound directly to the carbon atom(s) forming the alicyclic hydrocarbon ring. Furthermore, any epoxy compounds having 2 kinds or more of these epoxy groups in the molecule where the number of such epoxy groups totals more than one on the average. 
which is a substituted or unsubstituted glycidyl ether group wherein Z is a hydrogenatom, a methyl group or an ethyl group. 
which is a substituted or unsubstituted glycidyl ester group wherein Z is a hydrogen atom, a methyl group or an ethyl group. 
which is a substituted or unsubstituted 1,2-epoxypropyl group wherein Z is a hydrogen atom, a methyl group or an ethyl group.
The epoxy compounds containing more than one substituted or unsubstituted glycidyl ether groups on the average in the molecule, represented by the general formula (1), above, include substituted or unsubstituted glycidyl ether compounds obtainable by reacting an epihalohydrin with a polyhydric phenol compound such as bisphenol A, bisphenol F, bisphenol S, catechol, resorcinol, phenol novolak resin, resol resin or the like, or with a polyhydric alcohol compound such as a compound obtainable by subjecting glycerin, polyethylene glycol, or a polyhydric phenol compound to addition reaction with an alkylene oxide containing 2 to 4 carbon atoms.
The epoxy compounds having more than one substituted or unsubstituted glycidyl ester groups on the average in the molecule, represented by the general formula (2) above, include substituted or, unsubstituted glycidyl ester compounds obtainable by allowing an aliphatic polybasic carboxylic acid such as adipic acid, sebacic acid or the like, or an aromatic polybasic carboxylic acid such as phthalic acid, terephthalic acid or the like to react with an epihalohydrin.
The epoxy compounds having more than one N-substituted or unsubstituted 1,2-epoxypropyl groups on the average in the molecule, represented by the general formula (3) above, include substituted or unsubstituted glycidylamine compounds obtainable by allowing, e.g., 4,4xe2x80x2-diaminodiphenyl methane, aniline, m-aminophenol or the like to react with an epihalohydrin.
The epoxy compounds having more than one epoxy groups on the average in the molecule that are on the alicyclic hydrocarbon ring and/or that are bound directly to the carbon atom(s) forming the alicyclic hydrocarbon ring include, e.g., epoxy compounds represented by the following general formula (4) or (5). 
wherein Y represents an optionally substituted monocyclic, polycyclic or bridged cyclic hydrocarbon ring containing 2 to 8 carbon atoms. 
wherein Y has the same meanings as defined above in the general formula (4).
Examples of the epoxy compounds represented by the general formula (5) above may be those shown by the formulae (5-1) to (5-8) below. 
Further, the epoxy compounds having 2 kinds or more of these epoxy groups in the molecule wherein the total number of the epoxy groups is more than one on the average include substituted or unsubstituted glycidyl ether eater compounds obtainable by allowing a hydroxycarboxylic acid such as p-oxybenzoic acid, xcex2-oxynaphthoic acid or the like to react with an epihalohydrin, compounds having both a glycidyl ether group and an alicyclic epoxy group in the molecule as shown by the following formula (6), and the like. 
Further, these epoxy compounds may be accompanied by monoepoxy compounds within the range in which the effects of the invention are not inhibited. Such monoepoxy compounds include, e.g., monoepoxy compounds such as butyl glycidyl ether, phenyl glycidyl ether, p-tert-butyl phenyl glycidyl ether, sec-butyl phenyl glycidyl ether, and glycidyl methacrylate.
Epihalohydrin referred to herein is represented by the general formula (7) below, and includes, e.g., epichlorohydrin, epibromohydrin, 1,2-epoxy-2-methyl-3-chloropropane, 1,2-epoxy-2-ethyl-3-chloropropane, etc. 
wherein Z represents a hydrogen. atom, a methyl group or an ethyl group, and X represents a halogen atom.
Compounds (A) described above may be used each singly or in combination of two or more thereof.
Compound (B) as another starting material for synthetic reaction of the inventive latent curing agent for epoxy resin, that is, a compound having in the molecule both a tertiary amino group and at least one functional group selected from the group consisting of OH group, SH group, NH group, NH2 group, COOH group and CONHNH2 group is represented by, e.g., the following general formula (8). 
wherein W represents an OH group, SH group, NH group, NH2 group, COOH group or CONHNH2 group, R1 and R2 represent independently a C1 to C20 alkyl group, a C2 to C20 alkenyl group, an aralkyl group such as benzyl group, or one of the above groups wherein some carbon atom(s) in the carbon chain are replaced by other atom(s) (e.g., oxygen) or some hydrogen atom(s) on the carbon chain are replaced by a halogen, a functional group represented by W defined above or the like, and R3 is a similar to R1 and R2 defined above but divalent residue. Furthermore, R1 and R2 or R1, R2 and R3 may be bound to one another to form a ring.
As Compound (B), e.g., those compounds containing a tertiary amino group in the heterocyclic ring represented by the following general formula (9), (10) or (12) can also be mentioned as effective compounds. 
wherein R4, R5, R6 and R7 represent independently a hydrogen atom, one of the same groups as R1 and R2 defined in the general formula (8) above, an aryl group which may be substituted with an alkyl or aryl group, or a functional group represented by W in the general formula (8) above, and at least one of R4, R5, R6 and R7 represents a functional group represented by W or a group containing a functional group represented by W, except the case where R7 is a hydrogen atom. Even in the case where R7 is a hydrogen atom, R4, R5 and R6 can be a functional group represented by W or a group containing a functional group represented by W. 
wherein R8, R9 and R11 represent independently a hydrogen atom, one of the same groups as R1 and R2 defined in the general formula (8) above, or an aryl group which may be substituted with an alkyl or aryl group, R10 is a similar to R1 and R2 in the general formula (8) above but divalent residue, or an arylene group which may be substituted with an alkyl or aryl group, and Xxe2x80x2 is a hydrogen or a group represented by the following general formula (11): 
wherein R8 and R9 have the same meanings as in the general formula (10) above, and R12 is a hydrogen atom, one of the same groups as R1 and R2 defined in the general formula (8) above, or an aryl group which may be substituted with an alkyl or aryl group, and in the case where none of R11 and R12 are a hydrogen atom, at least one of R8, R9, R10, R11 and R12 represents a functional group represented by W or a group containing a functional group represented by W. Even in the case where R11 and/or R12 is a hydrogen atom, R8, R9, R10, R11 and R12 can be a functional group represented by W or a group containing a functional group represented by W. 
wherein R13 is a functional group represented by W, or a similar group to R1 or R2 but containing a functional group represented by W.
Such compound (B), that is, a compound containing, in the molecule, both tertiary amino group and at least one functional group selected from the group consisting of OH group, SH group, NH group, NH2 group, COOH group and CONHNH2 group, includes, e.g., 2-dimethylaminoethanol, 1-methyl-2-dimethylaminoethanol, 1-phenoxymethyl-2-dimethylaminoethanol, 2-diethylaminoethanol, 1-butoxymethyl-2-dimethylaminoethanol, 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-phenylimidazole, 1-aminoethyl-2-methylimidazole, 1-(2-hydroxy-3-phenoxypropyl)-2-methylimidazole, 1-(2-hydroxy-3-phenoxypropyl)-2-ethyl-4-methylimidazole, 1-(2-hydroxy-3-butoxypropyl)-2-methylimidazole, 1-(2-hydroxy-3-butoxypropyl)-2-ethyl-4-methylimidazole, 1-(2-hydroxy-3-phenoxypropyl)-2-phenylimidazoline, 1-(2-hydroxy-3-butoxypropyl)-2-methylimidazoline, 2-methylimidazoline, 2,4-dimethylimidazoline, 2-ethylimidazoline, 2-ethyl-4-methylimidazoline, 2-benzylimidazoline, 2-phenylimidazoline, 2-(o-tolyl)-imidazoline, tetramethylene-bis-imidazoline, 1,1,3-trimethyl-1,4-tetramethylene-bis-imidazoline, 1,3,3-trimethyl-1,4-tetramethylene-bis-imidazoline, 1,1,3-trimethyl-1,4-tetramethylene-bis-4-methylimidazoline, 1,3,3-trimethyl-1,4-tetramethylene-bis-4-methylimidazoline, 1,2-phenylene-bis-imidazoline, 1,3-phenylene-bis-imidazoline, 1,4-phenylene-bis-imidazoline, 1,4-phenylene-bis-4-methylimidazoline, 2-(dimethylaminomethyl)phenol, 2,4,6-tris(dimethylaminomethyl)phenol, N-xcex2-hydroxyethylmorpholine, 2-dimethyl aminoethane thiol, 2-mercaptobenzoimidazole, 2-mercaptobenzothiazole, 2-mercaptopyridine, 4-mercaptopyridine, N,N-dimethylaminobenzoic acid, N,N-dimethylglycine, nicotinic acid, isonicotinic acid, picolinic acid, N,N-dimethyl glycine hydrazide, nicotinic acid hydrazide, isonicotinic acid hydrazide, dimethyl aminopropyl amine, diethyl aminopropyl amine, dipropyl aminopropyl amine, dibutyl aminopropyl amine, dimethyl aminoethyl amine, diethyl aminoethyl amine, dipropyl aminoethyl amine, dibutyl aminoethyl amine, N-aminoethyl piperazine, dimethyl aminoethyl piperazine, diethyl aminoethyl piperazine, etc.
Compound (B) is preferably a compound having a tertiary amino group and at least one functional group selected from the group consisting ofOH group, NH groupand NH2 group.
Such compounds include tertiary amino group-containing alcohol compounds, such as 2-dimethylaminoethanol, 1-methyl-2-dimethylaminoethanol, 1-phenoxymethyl-2-dimethylaminoethanol, 2-diethylaminoethanol, 1-butoxymethyl-2-dimethylaminoethanol, N-xcex2-hydroxyethyl morpholine, 1-(2-hydroxy-3-phenoxypropyl)-2-methylimidazole, 1-(2-hydroxy-3-phenoxypropyl)-2-ethyl-4-methylimidazole, 1-(2-hydroxy-3-butoxypropyl)-2-methylimidazole, 1-(2-hydroxy-3-butoxypropyl)-2-ethyl-4-methylimidazole, 1-(2-hydroxy-3-phenoxypropyl)-2-phenylimidazoline, 1-(2-hydroxy-3-butoxypropyl)-2-methylimidazoline, etc.; tertiary amino group-containing phenol compounds such as 2-(dimethylaminomethyl)phenol, 2,4,6-tris(dimethylaminomethyl)phenol, etc.; and primary or secondary amino group-containing tertiary amine compounds such as 2-methylimidazoline, 2,4-dimethylimidazoline, 2-ethylimidazoline, 2-ethyl-4-methylimidazoline, 2-benzylimidazoline, 2-phenylimidazoline, 2-(o-tolyl)-imidazoline, tetramethylene-bis-imidazoline, 1,1,3-trimethyl-1,4-tetramethylene-bis-imidazoline, 1,3,3-trimethyl-1,4-tetramethylene-bis-imidazoline, 1,1,3-trimethyl-1,4-tetramethylene-bis-4-methylimidazoline, 1,3,3-trimethyl-1,4-tetramethylene-bis-4-methylimidazoline, 1,2-phenylene-bis-imidazoline, 1,3-phenylene-bis-imidazoline, 1,4-phenylene-bis-imidazoline, 1,4-phenylene-bis-4-methylimidazoline, dimethyl aminopropyl amine, diethyl aminopropyl amine, dipropyl aminopropyl amine, dibutyl aminopropyl amine, dimethyl aminoethyl amine, diethyl aminoethyl amine, dipropyl aminoethyl amine, dibutyl aminoethyl amine, N-aminoethyl piperazine, dimethyl aminoethyl piperazine, diethyl aminoethyl piperazine, etc.
Particularly preferable among these are tertiary amino group-containing alcohol compounds(and primary or secondary group-containing tertiary amine compounds.
More preferable examples of the tertiary amino group-containing alcohol compounds described above are those having 5- or 6-membered nitrogenous heterocyclic ring structure, such as 1-(2-hydrogy-3-phenoxypropyl)-2-methylimidazole, 1-(2-hydroxy-3-phenoxypropyl)-2-ethyl-4-methylimidazole, 1-(2-hydroxy-3-butoxypropyl)-2-methylimidazole, 1-(2-hydroxy-3-butoxypropyl)-2-ethyl-4-methylimidazole, 1-(2-hydroxy-3-phenoxypropyl)-2-phenylimidazoline, 1-(2-hydroxy-3-butoxypropyl)-2-methylimidazoline, etc., and particularly preferable are those having an imidazole skeleton, such as 1-(2-hydroxy-3-phenoxypropyl)-2-methylimidazole, 1-(2-hydroxy-3-phenoxylpropyl)-2-ethyl-4-methylimidazole, 1-(2-hydroxy-3-butoxypropyl)-2-methylimidazole, 1-(2-hydroxy-3-butoxypropyl)-2-ethyl-4-methylimidazole, etc.
More preferable examples of the primary or secondary group-containing tertiary amine compounds described above are those having a 5- or 6-membered nitrogenous heterocyclic ring structure, such as 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-phenylimidazole, 1-aminoethyl-2-methylimidazole, 2-methylimidazoline, 2,4-dimethylimidazoline, 2-ethylimidazoline, 2-ethyl-4-methylimidazoline, 2-benzylimidazoline, 2-phenylimidazoline, 2-(o-tolyl)-imidazoline, tetramethylene-bis-imidazoline, 1,1,3-trimethyl-1,4-tetramethylene-bis-imidazoline, 1,3,3-trimethyl-1,4-tetramethylene-bis-imidazoline, 1,1,3-trimethyl-1,4-tetramethylene-bis-4-methylimidazoline, 1,3,3-trimethyl-1,4-tetramethylene-bis-4-methylimidazoline, 1,2-phenylene-bis-imidazoline, 1,3-phenylene-bis-imidazoline, 1,4-phenylene-bis-imidazoline, 1,4-phenylene-bis-4-methylimidazoline, N-aminoethyl piperazine, dimethyl aminoethyl piperazine, diethyl aminoethyl piperazine, etc., and particularly preferable are those having an imidazole skeleton, such as 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-phenylimidazole and 1-aminoethyl-2-methylimidazole, etc.
Compounds (B) described above may be used each singly or can be used in combination of two or more thereof, to react with Compound (A).
Compound (C) as the remaining starting material for the synthetic reaction of the inventive latent curing agent for epoxy resin, that is, a compound having in the molecule at least one functional group selected from the group consisting of NH2 group and CONHNH2 group, or in the molecule at least 2 functional groups selected from the group consisting of OH group, SH group, NH group, NH2 group, COOH group and CONHNH2 group (provided that those compounds having an epoxy group or a tertiary amino group in the molecule are excluded), includes, e.g., amine compounds such as piperazine, aniline and cyclohexyl amine; polybasic carboxylic acids such as adipic acid, phthalic acid, 3,9-bis(2-carboxyethyl)-2,4,8,10-tetraoxaspiro [5,5] undecane; polyvalent thiols such as 1,2-dimercaptoethane and 2-mercaptoethyl ether; hydrazide compounds such as phenyl acetic acid hydrazide; amino acids such as alanine and valine; compounds having 2 kinds or more of functional groups, such as 2-mercaptoethanol, 1-mercapto-3-phenoxy-2-propanol, mercaptoacetic acid, N-methyl ethanol amine, diethanol amine, hydroxyaniline, N-methyl-o-aminobenzoic acid, anthranilic acid, sarcosine, hydroxybenzoic acid and lactic acid; polyhydric alcohols such as pentaerythritol, sorbitol, trimethylolpropane, trimethylolethane and tris (hydroxyethyl) isocyanurate; and polyhydric phenols.
Compound (C) is particularly preferably a polyhydric phenol compound, and examples thereof can be bisphenol A, bisphenol F, bisphenol S, hydroquinone, catechol, resorcinol, pyrogallol, phenol novolak resin and resol resin.
Compounds (C) described above may be used each singly or can be used in combination of two or more thereof, to react with Compounds,(A) and (B).
In the case where the inventive curing agent for epoxy resin is to be obtained by reacting the two compounds i.e., Compounds (A) and (B), when Compound (B) is a compound having in the molecule both a tertiary amino group and at least one functional group selected from the group consisting of OH group, SH group, COOH group and CONHNH2 group, then the ratio of the respective compounds to be used for producing the curing agent for epoxy resin is a ratio of 0.8 to 2.5 equivalents, preferably 0.9 to 1.5 equivalents of the epoxy group of Compound (A) per 1 equivalent of the active hydrogen in the active hydrogen-containing functional group (i.e., the OH group, SH group, COOH group and CONHNH2 group) of Compound (B), in other words, Compounds (A) and (B) are allowed to react on each other in such ratio that Compound (A) in an amount of 0.8 to 2.5 equivalents, preferably 0.9 to 1.5 equivalents in terms of the epoxy group thereof is allowed to react on Compound (B) in an amount of 1 equivalent in terms of the active hydrogen in the active hydrogen-containing functional group thereof. If the amount of the epoxy group is less than 0.8 equivalents per 1 equivalent of the active hydrogen, then the softening temperature of the resulting latent curing agent for epoxy resin is low, its grinding is difficult, and upon incorporation thereof as the latent curing agent into an epoxy compound, sufficient storage stability cannot be obtained, while given 2.5 equivalents or more, the softening temperature of the reaction product gets too high, and upon incorporation thereof as the latent curing agent into an epoxy compound, sufficient rapid curing properties are not exhibited while the resulting cured product becomes heterogeneous. Further, in the same case, when Compound (B),is a compound having in the molecule both a tertiary amine group and at least functional group selected from the group consisting of NH group and NH2 group, the ratio for this reaction is a ratio of 0.4 to 1.1 equivalents of the epoxy group of Compound (A) to 1 equivalent of the active hydrogen of the active hydrogen-containing functional group (i.e., NH group and NH2 group) of Compound (B). This is because if the epoxy group of Compound (A) is in an amount of less than 0.4 equivalents, sufficient storage stability cannot be obtained upon incorporation of the resulting reaction product as the latent curing agent into an epoxy compound, while given 1.1 equivalents or more, there occurs gelation during the addition reaction. Incidentally, with respect to the relationship in equivalence between active hydrogen and epoxy group, 1 epoxy group corresponds to 1 active hydrogen atom.
In the case where the 3 compounds, that is, Compound (A), Compound (B) and Compound (C) are to be used to produce the curing agent for epoxy resin, when Compound (B) is a compound having in the molecule, both a tertiary amino group (and at least one functional group selected from the group consisting of OH group, SH group, COOH group and CONHNH2 group, then the ratio of the respective compounds to be used for producing the curing agent for epoxy resin is a ratio of 0.5 to 2.5 equivalents, preferably 0.6 to 1.5 equivalents of the epoxy group of Compound (A) per 1 equivalent of the total active hydrogen in both Compounds (B) and (C), and simultaneously Compound (C) is used preferably in an amount of 2-fold moles or less relative to Compound (B). Less than 0.5 equivalents of the epoxy group from Compound (A) does not give sufficient storage stability upon incorporation of the resulting reaction product as the latent curing agent into an epoxy compound, while given 2.5 equivalents or more, the softening temperature of the reaction product gets too high, and upon incorporation thereof as the latent curing agent into an epoxy compound, sufficient rapid curing is not exhibited while the resulting cured product becomes heterogeneous. Further, if Compound (C) exceeds 2-fold moles relative to Compound (B), curing properties are worsened. In addition, in the same case where the 3 compounds, i.e., Compounds (A), (B) and (C) are to be used to produce the curing agent for epoxy resin, when Compound (B) is a compound having, in the molecule, both a tertiary amino group and at least one functional group selected from the group consisting of NH group and NH2 group, then the ratio of the respective compounds to be used is a ratio of 0.2 to 1.1 equivalents of the epoxy group in Compound (A) per 1 equivalent of the total active hydrogen in both Compounds if (B) and (C). If the epoxy group from Compound (A) is less than 0.2 equivalent, sufficient storage stability cannot be attained upon incorporation of the resulting reaction product as the latent curing agent into an epoxy compound, while in an amount of more than 1.1 equivalents, the softening temperature of the reaction product gets too high, and upon incorporation thereof as the latent curing agent, there does not occur sufficiently rapid curing while the resulting cured product is rendered heterogeneous.
The 2 compounds, i.e., Compounds (A) and (B) or the 3 compounds, i.e., Compounds (A), (B) and (C) are allowed to react on each other or one another in the presence of 0.05 to 5.0 equivalents, preferably 0.1 to 2.0 equivalents of water, per 1 equivalent of the epoxy group of Compound (A), whereby the inventive latent curing agent for epoxy resin can be obtained. Usually, trace amounts of water are also contained in Compounds (A), (B) and (C) as the starting materials but are insufficient to achieve the effects of the present invention. According to the present invention, water is further added for reaction in an amount of 0.05 to 5.0 equivalents per 1 equivalent of the epoxy group in Compound (A), whereby the inventive latent curing agent for epoxy resin can be obtained. If the amount of water is less than 0.05 equivalents, sufficient storage stability cannot be achieved upon incorporation of the resulting reaction product as the latent curing agent into an epoxy compound, while an amount of 5.0 or more equivalents is not practical because the more time and energy are required to remove the excessive water after reaction and before grinding.
The inventive curing agent for epoxy resin can be obtained as addition products having arbitrary softening temperatures by changing the kind and mixing ratio of Compounds (A), (B) and (C) and the ratio of water for reaction, and those having softening temperatures of 60 to 180xc2x0 C. are preferable. If the latent curing agent with a softening temperature of less than 60xc2x0 C. is incorporated into an epoxy compound, the resulting epoxy resin composition is inferior in storage stability at room temperature, while the latent curing agent with a softening temperature of more than 180xc2x0 C. does not bring about sufficient curing property.
The inventive latent curing agent for epoxy resin can be obtained, e.g., by sufficiently mixing Compound (A), Compound (B) and water, or Compound (A), Compound (B), Compound (C) and water, gelatinizing the mixture at room temperature, completing the reaction at a temperature of 80 to 150xc2x0 C., then solidifying the resulting reaction mixture by cooling, and grinding the solidified mixture. This reaction may be conducted in a solvent such as toluene, tetrahydrofuran, methyl ethyl ketone or dimethylformamide, followed by removing the solvent, solidification and grinding. Further, water may be either completely dissolved in, or dispersed without being completely dissolved in, Compounds (A) and (B), or Compounds (A), (B) and (C), or these compounds to which a solvent has been added.
The inventive latent curing agent for epoxy resin can also be used in combination with curing agents known in the art, such as acid anhydrides, dicyandiamide, hydrazide compounds, guanamines, melamines, etc.
The inventive latent curing agent for epoxy resin can be put in commercial distribution as such or after added with a curing agent known in the art.
Further, the inventive curable epoxy resin composition is a resin composition comprising (x) an epoxy compound having more than one (1) epoxy groups on the average in the molecule and (y) an inventive latent curing agent for epoxy resin, as the essential ingredients.
The epoxy compound (x) having more than one epoxy groups on the average in the molecule can be completely the same as Compound (A) as referred to above, that is, the epoxy compound having more than one epoxy groups on the average in the molecule, and various compounds known in the art, such as those illustrated above, can be mentioned. The amount of the inventive curing agent for epoxy resin to be used (incorporated) in the inventive resin composition is preferably 0.3 to 50 parts by weight relative to 100 parts by weight of the epoxy compound (x). An amount of less than 0.3 part by weight cannot provide sufficient curable properties to the resulting resin composition, while an amount of more than 50 parts by weight may reduce the performance of the cured product. Further, other additives can be added, if necessary or desired, to the curable epoxy resin composition of the present invention. Such additives include, e.g., (z) fillers such as alumina, silica, aerozil, calcium carbonate, aluminum hydroxide, magnesium hydroxide, talc, bentonite, barium sulfate, and the like (inorganic fillers), and fluidity regulators such as acryl oligomers, silicone etc., surface modifiers, diluents, and flame-retardants.
Hereinafter, the above-mentioned econd invention will be described.
Compound (a) for the inventive latent curing agent for epoxy resin, that is, an alicyclic epoxy compound having 2 or more epoxy groups in the molecule, includes those epoxy compounds having 2 or more epoxy groups on the average in the molecule that are bound directly to the carbon atom(s) forming the alicyclic hydrocarbon ring and/or that are on the alicyclic hydrocarbon ring.
For example, mention can be made of those epoxy compounds having 2 or more epoxy groups in the molecule represented by the general formula (1) or (2) below. 
wherein Y represents a C2 to C8 monocyclic, polycyclic or bridged hydrocarbon ring which may have substituent group(s).
Specific examples thereof include, e.g., those epoxy compounds-represented by the formulae (i) to (vii) below. 
wherein R1 and R2 represent independently a hydrogen atom, a methyl group or an ethyl group. 
wherein R3 and R4 represent independently a hydrogen atom, a methyl group or an ethyl group, and n is an integer of 2 to 10.
Among these epoxy compounds, those alicyclic epoxy compounds represented by the formulae (vi) and (vii) are particularly preferable because of their high boiling point, and those alicyclic epoxy compounds represented by the formula (vi) are more preferable because of their low viscosity.
As an alicyclic epoxy compound represented by the formula (vi) above, xe2x80x9cCeloxide 2021xe2x80x9d produced by Daicel Chemical Industries, Ltd. (in the formula (vi), R1 and R2 are both a hydrogen atom) is commercially available, and as an alicyclic epoxy compound represented by the formula (vii), xe2x80x9cERL-4299xe2x80x9d produced by Union Carbide (in the formula (vii), R3 and R4 are both a hydrogen atoms, and n=4) or the like is commercially available.
The alicyclic epoxy compounds described above may be used each alone or in combination of two or more thereof.
A hydrolyzable halogen group contained in an epoxy resin is a critical factor worsening electrical reliability, so in epoxy resin compositions used in the electronics field, particularly in producing semiconductor parts, its concentration should be made as low as possible. In conventional latent curing agents, glycidyl compounds have been generally used as epoxy compounds, but the glycidyl compounds usually contain hydrolyzable halogen groups in the order of 1000 ppm (weight) and can thus not be said to be preferable in respect of electrical reliability in the field of electronics. Further, the hydrolyzable halogen groups can also be reduced by refining, but it is difficult to attain high purity, and if refining is conducted, there are the problems of an increased number of steps, higher costs, etc. The alicyclic epoxy compounds do inherently not contain hydrolyzable halogen groups, and are free from the problems described above, thus enable a significant reduction of the hydrolyzable halogen groups in the latent curing agent.
Compound (b) for the inventive latent curing agent for epoxy resin, that is, a compound having in the molecule both a tertiary amino group and at least one functional group selected from the group consisting of OH group, SE group, NH group, NH2 group, COOH group and CONHNH2 group is represented by, e.g., the general formula (3) below. Incidentally, the general formula (3) corresponds to the general formula (8) previously described in connection with the first invention. 
wherein W represents an OH group, SH group, NH group, NH2 group, COOH group or CONHNH2 group, R5 and R6 represent independently a C1 to C20 alkyl group, a C2 to C20 alkenyl group, an aralkyl group such as benzyl group, or one of the above groups wherein some carbon atom(s) in the carbon chain are replaced by other atom(s) (e.g., oxygen) or some hydrogen atom(s) on the carbon chain are replaced by a halogen, a functional group represented by W defined above or the like, and R7 is a similar to R5 and R6 defined above but divalent residue. Furthermore, R5 and R6 or R5, R6 and R7 may be bound to one another to form a ring.
As Compound (b), those compounds containing a tertiary amino group in the heterocyclic ring represented by the following general formula (4), (5) or (7) can also be mentioned as effective compounds. Incidentally, the general formulae (4), (5) and (7) correspond, respectively, to the general formulae (9), (10) and (12) described above in connection with the first invention. 
wherein R8, R9, R10 and R11 represent independently a hydrogen atom, one of the same groups as R5 and R6 defined in the general formula (3) above, an aryl group which may be substituted with an alkyl or aryl group, or a functional group represented by W in the general formula (3) above, and at least one of R8, R9, R10 and R11 represents a functional group represented by W or a group containing a functional group represented by W except the case where R11 is a hydrogen atom. Even in the case where R11 is a hydrogen atom, R8, R9 and R10 can be a functional group represented by W or a group containing a functional group represented by W. 
wherein R12, R13 and R15 represent independently a hydrogen atom, one of the same group as R5 and R6 defined in the general formula (3) above, or an aryl group which may be substituted with an alkyl or aryl group, R14 is a similar to R5 and R6 in the general formula (3) above, but divalent residue, or an arylene group which may be substituted with an alkyl or aryl group, and Xxe2x80x2 is a hydrogen or a group represented by the following general formula (6): 
wherein R12 and R13 have the same meanings as in the general formula (5) above, and R16 is a hydrogen atom, one of the same group as R5 and R6 defined in the general formula (3) above, or an aryl group which may be substituted with an alkyl or aryl group, and in the case where none of R15 and R16 are a hydrogen atom, at least one of R12, R13, R14, R15 and R16 represents a functional group represented by W or a group containing a functional group represented by W. Even in the case where R15 and/or R16 is a hydrogen atom, R12, R13, R14, R15 and R16 can be a functional group represented by W or a group containing a functional group represented by W. Incidentally, the general formula (6) above, corresponds to the general formula (11) described above in connection with the first invention. 
wherein R17 is a functional group represented by W, or a similar group to R5 or R6 but containing a functional group represented by W.
Specific examples of Compound (b) can be the same as those of Compound (B) described earlier in connection with the first invention.
As Compound (b) are preferable compounds having both a tertiary amino group and at least one functional group selected from the group consisting of OH group, NH group and NH2 group, which is all the same as with Compound (B). And specific examples and more preferable examples of such compounds are all the same as with Compound (B).
Compound (b) as described above can be used each singly or in combination of two or more thereof.
Compound (c) as one of the starting materials for the synthetic reaction of the inventive latent curing agent for epoxy resin, that is, a compound having in the molecule at least one functional group selected from the group consisting of NH2 group and CONHNH2 group, or in the molecule at least 2 functional groups selected from the group consisting of OH group, SE group, NH group and COOH group (provided that those compounds having an epoxy group or a tertiary amino group in the molecule are excluded), includes, e.g., amine compounds such as piperazine, aniline and cyclohexyl amine; polybasic carboxylic acids such as adipic acid, phthalic acid, 3,9-bis(2-carboxyethyl)-2,4,8,10-tetraoxaspiro [5,5] undecane; polyvalent thiols such as 1,2-dimercaptoethane and 2-mercaptoethyl ether; hydrazide compounds such as phenyl acetic acid hydrazide; amino acids such as alanine and valine; compounds having 2 kinds or more of functional groups, such as 2-mercaptoethanol, 1-mercapto-3-phenoxy-2-propanol, mercaptoacetic acid, N-methyl ethanol amine, diethanol amine, hydroxyaniline, N-methyl-o-aminobenzoic acid, anthranilic acid, sarcosine, hydroxybenzoic acid and lactic acid; polyhydric alcohols such as pentaerythritol, sorbitol, trimethylolpropane, trimethylolethane and tris(hydroxyethyl) isocyanurate; and polyhydric phenols. These compounds are all the same as with Compound (C).
Compound (c) is particularly preferably a polyhydric phenol compound, and examples thereof can be bisphenol A, bisphenol F, bisphenols, hydroquinone, catechol, resorcinol, pyrogallol, phenol novolak resin and resol resin, which is all the same as with Compound (C).
Compounds (c) described above may be used each singly or can be used in combination of two or more thereof, to react with Compounds (a) and (b).
It is not preferable that none of Compounds (b) and (c) contain any of OH group, SH group, COOH group and CONHNH2 group, because the reactivity between the alicyclic epoxy compounds and these compounds is significantly worsened. Further, Compounds (b) and (c), unlike glycidyl compounds, do inherently not contain hydrolyzable halogen groups.
To produce the inventive latent curing agent for epoxy resin, Compounds (a), (b) and (c) and optionally, Compound (d), a glycidyl compound having 2 or more epoxy groups in the molecule can be allowed to react on one another. In this case, the reaction temperature and reaction time can be reduced in producing the inventive latent curing agent for epoxy resin, and there is, in turn, an advantage from the viewpoint of productivity of the latent curing agent for epoxy resin. However, the addition or use of the glycidyl compounds, as described above, causes an increase in hydrolyzable halogen atoms in the latent curing agent, resulting in a reduction in the effects of the present invention, so whether they are used or not, or what amount is to be used, shall be determined suitably in consideration of the desired use, standards, total costs, etc. For example, if the inventive latent curing agent for epoxy resin is to be. used in conducting composites, the amount of glycidyl compounds to be used or added is preferably not more than 30% by weight relative to the total amount of Compound (a).
If the glycidyl compounds are to he used or added, those with hydrolyzable halogen groups reduced by refining may be used, but the use or addition thereof may result in the increase of production costs, so whether they are added or not shall be suitably determined depending on the given circumstances.
The above Compound (d), that is, the glycidyl compound having 2 or more epoxy groups in the molecular, includes polyglycidyl ether compounds, polyglycidyl ester compounds, polyglycidyl amine compounds, glycidyl ether ester compounds, and compounds having glycidyl ester group(s) and alicyclic epoxy group(s) in the molecule as shown by the formula (8). 
The polyglycidyl ether compounds described above include, e.g., glycidyl ether compounds obtainable by reacting an epihalohydrin with a polyhydric phenol compound such as bisphenol A, bisphenol F, bisphenol S, catechol, resorcinol, phenol novolak resin or resol resin, or with a polyhydric alcohol compound such as a compound obtainable by subjecting glycerin, polyethylene glycol, or polyhydric phenol compound to addition reaction with an alkylene oxide containing 2 to 4 carbon atoms.
As the polyglycidyl ester compounds described above, mention can be made of glycidyl ester compounds obtainable by allowing an aliphatic polycarboxylic acid such as adipic acid, sebacic acid or the like, or an aromatic polycarboxylic acid such as phthalic acid, terephthalic acid or the like, to react on an epihalohydrin.
As the above polyglycidyl amine compounds, mention can be made of glycidylamine compounds, etc. obtainable by reacting, e.g., 4,4xe2x80x2-diaminodiphenyl methane, aniline, m-aminophenol or the like, with an epihalohydrin.
As the above glycidyl ether ester compounds, mention can be made of, e.g., glycidyl ether ester compounds obtainable by allowing a hydroxycarboxylic acid such as p-oxybenzoic acid, xcex2-oxynaphthoic acid or the like, to react with an epihalohydrin.
Epihalohydrin referred to herein includes, e.g., epichlorohydrin, epibromohydrin, 1,2-epoxy-2-methyl-3-chloropropane, 1,2-epoxy-2-ethyl-3-chloropropane, etc.
Among the glycidyl compounds described above, the glycidyl ether compounds, glycidyl ester compounds and glycidyl ether ester compounds are preferable, among which the glycidyl ether compounds are particularly preferable.
The glycidyl compounds mentioned above may be used each singly or can be used in combination of the 2 kinds or more thereof.
In the production of the inventive latent curing agent for epoxy resin, when Compound (b) is a compound having in the molecule a tertiary amino groupand at least one functional group selected from the group consisting of OH group, SH group, COOH group and CONHNH2 group, the ratio of the respective compounds is a ratio of 0.5 to 2.5 equivalents, preferably 0.6 to 1.5 equivalents of the epoxy groups in Compound (a) (or in both Compounds (a) and (d)) per 1 equivalent of all of the OH group, SH group, COOH and CONHNH2 group in Compounds (b) and (c) (provided that with respect to the CONHNH2 group, a number obtained by doubling the number of moles of the CONHNH2 group is assumed to be the equivalent of the CONHNH2 group because the CONHNH2 group is a di-functional group toward the epoxy compound), and Compound (c) is used preferably in twice the amount in terms of moles of Compound (b). If the epoxy group in Compound (a) (or in both Compounds (a) and (d)) is less than 0.5 equivalent, sufficient storage stability cannot be obtained upon incorporation of the reaction product as the latent curing agent into an epoxy compound, whereas given 2.5 equivalents or more, the softening temperature of the reaction product gets too high and upon incorporation thereof as the latent curing agent into an epoxy compound, sufficient rapid curing properties cannot be exhibited while the resulting cured product becomes heterogeneous. If Compound (c) exceeds twice the moles of Compound (b), curing properties are worsened.
When Compound (b) is a compound having in the molecule a tertiary amino group and at least one functional group selected from the group consisting of NH group and NH2 group, the ratio of the respective compounds is a ratio of 0.2 to 1.1 equivalents of the epoxy group in Compound (a) (or in both Compounds (a) and (d)) per 1 equivalent of all of the OH group, SH group, COOH, CONHNH2 group, NH group and NH2 group in Compounds (b) and (c) (provided that with respect to the CONHNH2 group and NH2 group, a number obtained by doubling the number of moles of the CONHNH2 group or NH2 group is assumed to be the equivalent of the CONHNH2 group or NH2 group because these groups are di-functional groups toward the epoxy compound). If the epoxy group in Compound (a) (or in both Compounds (a) and (d)) is less than 0.2 equivalent, sufficient storage stability cannot be obtained upon incorporation of the reaction product as the latent curing agent into an epoxy compound, whereas given 1.1 equivalents or more, the softening temperature of the reaction product gets too high and upon incorporation thereof as the latent curing agent into an epoxy compound, sufficient rapid curing properties cannot be exhibited while the resulting cured product becomes heterogeneous.
The inventive latent curing agent for epoxy resin can be obtained, e.g., by sufficiently mixing Compounds (a), (b) and (c) (or Compounds (a), (b), (c) and (d)), gelatinizing the mixture at room temperature, then completing the reaction at a temperature of 80 to 150xc2x0 C., then solidifying by cooling, and grinding the solidified mixture. This reaction may be conducted in a solvent such as toluene, tetrahydrofuran, methyl ethyl ketone, dimethylformamide or the like, followed by removal of the solvent, solidification and grinding.
The inventive latent curing agent for epoxy resin can be obtained as the addition products having arbitrary softening temperatures by changing the type and mixing ratio of Compounds (a), (b) and (c) (or (a), (b), (c) and (d)), and those having softening temperatures of 60 to 180xc2x0 C. are more preferable. If the latent curing agent with a softening temperature of less than 60xc2x0 C. is incorporated into an epoxy compound, the resulting epoxy composition is poor in storage stability at room temperature while the latent curing agent with a softening temperature of more than 180xc2x0 C. does not bring about sufficient curing property.
In producing the inventive latent curing agent for epoxy resin, monoepoxy compounds,besides Compounds (a), (b), (c) and (d) may accompany in the range in which the effects of the present invention are not inhibited. Such monoepoxy compounds include, e.g., monoepoxy compounds such as butyl glycidyl ether, phenyl glycidyl ether, p-tert-butyl phenyl glycidyl ether, sec-butyl phenyl glycidyl ether, glycidyl methacrylate, etc.
The latent curing agent for epoxy resin of the present invention can also be used in combination with curing agents known in the art, such as acid anhydrides, dicyandiamide, hydrazide compounds, guanamines, melamines, etc.
The respective compounds as the starting materials for the inventive latent curing agent for epoxy resin, some of which have been described above, may be refined suitably in conventional processes such as distillation, recrystallization, etc.
The inventive latent curing agent for epoxy resin is rapidly curing or has rapidly curing function at low temperatures and does not require high temperatures for adhesion, thus reducing thermal stress on electronics parts such as electronic elements, liquid-crystal panels, etc., to which the latent curing agent when incorporated into an epoxy compound has been applied, whereby the reduction and deterioration of connection precision can be reduced. Further, it is rapidly curing at low temperatures and simultaneously, has the following excellent characteristics as compared with conventional amine adduct-type latent curing agents: (1) it is also excellent in electrical reliability due to a low concentration of hydrolyzable halogen groups therein; (2) it raises the glass transition point of the resulting resin to improve the thermostability of the cured product; and (3) when used in conducting composites, it improves the electrical conductivity of the cured product.
The inventive latent curing agent (yxe2x80x2) for epoxy resin can be uniformly mixed with an epoxy compound (xxe2x80x2) having 2 or more epoxy groups in the molecule, whereby the curable epoxy resin composition of the present invention is easily formed.
In the curable epoxy resin composition of the present invention, the epoxy compound (xxe2x80x2) having 2 or more epoxy groups in the molecule includes a wide variety of epoxy compounds such as alicyclic epoxy compounds used as Compound (a) or glycidyl compounds used as Compound (d). In the field of electronics, glycidyl compounds with hydrolyzable halogen groups reduced by refining are used, and the inventive latent curing agent for epoxy resin can also be formed into a curable epoxy resin composition having a low content of hydrolyzable halogen groups, which is more-suitable for use in electronics.
The amount of the inventive. latent curing agent (yxe2x80x2) for epoxy resin to be incorporated in the inventive curable epoxy resin composition is preferably 0.3 to 50 parts by weight per 100 parts by weight of the epoxy compound (xxe2x80x2) having 2 or more epoxy groups in the molecule. In an amount of less than 0.3 part by weight, sufficient curing properties cannot be attained, while in an amount of more than 50 parts by weight, the performance of the resulting cured product may be worsened.
By further adding inorganic filler(s) (zxe2x80x2) to the curable epoxy resin composition consisting of the components (yxe2x80x2) and (xxe2x80x2) described above, it is possible to form the curable epoxy resin composition to be used as, e.g., resin composition for conducting composites, anisotropic conductive films, encapsulants for semiconductor, or the like.
To use the inventive resin composition as a resin composition for conductive resin composities or anisotropic conductive films, the inorganic fillers include conductive fillers, that is, metal powder such as gold, silver, copper, palladium, nickel, etc., as well as carbon black, graphite, etc. Further, it is also possible to use composite fillers wherein metal powder such as iron, copper, nickel, etc. or carbon black, silica powder, organic resin powder such as polystyrene, is surface-coated with an electrically conductive material such as gold, silver, or the like. Such fillers may be in the form of granules, flakes, dendrites or the like, as is necessary. Usually, silver powder is often used from the viewpoint of costs and electrical conductance.
To use the inventive resin composition as encapsulant resin for semiconductor, the inorganic fillers include powders of alumina, silica, calcium carbonate, aluminum hydroxide, in magnesium hydroxide, talc, bentonite, barium sulfate, aerozil, etc. In particular, silica such as crystalline silica, fused silica, or the like, is frequently used.
To use the inventive resin composition as, e.g., resin composition for conducting composites, the amount of inorganic fillers to be incorporated is 10 to 55 volumes per 100 volumes of the inventive resin composition. In an amount of less than 10 volumes, sufficient electrical conductance cannot be achieved, while in an amount of more than 55 volumes, the viscosity of the resin composition gets too viscous to be practical. A preferable amount is 15 to 55 volumes. To use the inventive resin composition as resin composition for anisotropic conductive films, the amount of inorganic fillers to be incorporated is 0.1 to 25 volumes per 100 volumes of the film and more preferably 0.1 to 10 volumes to prevent an excess of the electrically conductive inorganic fillers from forming a short circuit. Further, for use thereof as encapsulant resin for semiconductor, the amount of inorganic fillers is 40 to 90 parts by weight per 100 parts by weight of the resin excluding the fillers.
Besides the inorganic fillers described above, organic fillers usually incorporated into curable epoxy resin composition can also be incorporated within the range in which the effects of the present invention are not inhibited. Such organic fillers include fine nylon particles, fine polystyrene particles, fine polyethylene particles, cross-linked fine rubber particles, fine acrylic core-shell particles, fine rubber-based core-shell particles, fine silicone particles, and fine ethylene-acrylate copolymer particles.
The curable epoxy resin composition of the present invention can contain other additives as necessary within the range in which the effects of the present invention are not inhibited. Such additives include, e.g., fluidity regulators such as acrylic oligomer, silicone, etc., as well as surface modifiers, coloring agents, releasing agents, surface active agents, coupling agents, diluents, flame-retardants, silicon oil, rubber, etc.